Does this mean that: Can I license multiple 16core servers with the same license?
You can ONLY use this license on one SQL Server machine, on this same machine you can install multiple instances of sql server without paying for new instances. If you want to use it on other machine having sql server you need to stop this machine and then use it on other.
Can I use the same license on servers with less core?
Yes you can but then you are wasting money, aren't your ?
PS: You should get this cross checked with licensing expert. This is technical forum and I am replying you after reading online available MS licensing guide.